We did this same experiment in school, with a tiny pinprick of oil, estimating the volume of the drop as a sphere, and a small water tank, and then estimated the area of oil slick as a circle.
I've stayed in over fifty Airbnb in the last three years. Only three haven't worked out (misleading apartment, mouse-poop kitchen, unresponsive host). Each time Airbnb has sorted me out with a refund, called me to discuss the problem, helped finding an alternative place, and providing a voucher to cover any price gap.
If you're certain it's what you want, don't accept no for an answer and keep hassling the school or college at different levels and see if you can still make it happen.
Similarly, the manual that came with the original ZX Spectrum rubber key version was awesome, with a complete description of Sinclair BASIC and all the Z80 assembler op codes for good luck. The 48k+ manual that followed was nowhere near as useful.
Make sure you are paid and bonused properly regardless of any future exit, because most startups never get there. In CTO role you should get something at the exit too, because you are likely to be instrumental in that success. Because companies often pivot or your part of the company changes outside of your control, you should have both.